Enable tab focus change in notes field.

Previously, if focus landed inside the Notes field in the Entry editor,
hitting 'tab' would insert a literal tab character. This is problematic
for those using screen readers. Now, hitting tab goes to the next
widget in the focus list.

Fixes keepassxreboot#4222.

src/gui/entry/EditEntryWidgetMain.ui

@@ -192,6 +192,9 @@
      <property name="accessibleName">
       <string>Notes field</string>
      </property>
+     <property name="tabChangesFocus">
+      <bool>true</bool>
+     </property>
     </widget>
    </item>
    <item row="9" column="1">